Organic electroluminescent materials and devices

ABSTRACT

Novel organic compounds comprising ligands with deuterium substitution are provided. In particular, the compound is an iridium complex comprising methyl-d3 substituted ligands. The compounds may be used in organic light emitting devices to provide devices having improved color, efficiency and lifetime.

This application is a continuation of co-pending U.S. patent application Ser. No. 15/452,994, filed Mar. 8, 2017, which is a continuation of U.S. patent application Ser. No. 13/960,264, filed Aug. 6, 2013, now U.S. Pat. No. 9,634,265, which is a continuation of U.S. patent application Ser. No. 12/768,068, filed Apr. 27, 2010, now U.S. Pat. No. 8,557,400, which claims priority to U.S. Provisional Application Ser. No. 61/173,346, filed Apr. 28, 2009, the entire disclosures of which are herein expressly incorporated by reference.

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

FIELD OF THE INVENTION

The present invention relates to novel organic compounds that may be advantageously used in organic light emitting devices. More particularly, the invention relates to novel methyl-d₃ substituted iridium complexes and their use in OLEDs.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

A compound comprising a ligand having the structure:

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. Preferably, A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine. Preferably, B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40. Preferably, the metal is Ir.

In one aspect, the ligand has the structure:

In one aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl. In another aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.

In one aspect, compounds are provided wherein at least one of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.

In particular, compounds are provided comprising a ligand wherein the ligand is selected from the group consisting of:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ is CD₃.

In another aspect, compounds comprise a ligand selected from Formula II, III, IV, V, VI, and VII. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ includes CD₃.

In yet another aspect, compounds are provided comprising a ligand selected from the group consisting of:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be linked. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be fused. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ includes an alkyl group that includes CD, CD₂, or CD₃.

Specific examples of methyl-deuterium substituted (also referred to herein as methyl-d3 or CD₃) iridium complexes are provided, and include compounds selected from the group consisting of Compounds 2-42. In one aspect, compounds are provided wherein the compound comprises a ligand having Formula II, for example, Compounds 2-4. In another aspect, compounds are provided wherein the compound comprises a ligand having Formula III, for example, Compounds 5-9. In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula IV, for example, Compounds 10-14 and 27-40. In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula V, for example, Compounds 15-19. In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula VI, for example, Compounds 20-23. In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula VII, for example, Compounds 24-26, 41, and 42.

Additional specific example of deuterium substituted compounds include compounds selected from the group consisting of Compound 43-Compound 67, Compound 69-Compound 82. In one aspect, compounds are provided wherein the compound comprises a ligand having Formula III, for example, Compounds 58, 59, 69-70 and 75-77. In another aspect, compounds are provided wherein the compound comprises a ligand having Formula IV, for example, Compounds 43-52, 62-67, and 80-82. In yet another aspect, compounds are provided wherein the compound comprises a ligand having Formula V, for example, Compounds 55-57, 73 and 74. In a further aspect, compounds are provided wherein the compound comprises a ligand having Formula VI, for example, Compounds 60, 61, 78 and 79. In yet another aspect, compounds are provided wherein the compound comprises a ligand having Formula VIII, for example, Compounds 53, 54, 71 and 72.

In one aspect, homoleptic compounds are provided. In particular, compounds are provided wherein the ligand having FORMULA I is in a ligand in a homoleptic compound. In another aspect, heteroleptic compounds are provided. In particular compounds are provided wherein the ligand having FORMULA I is a ligand in a heteroleptic compound.

An organic light emitting device is also provided. The device may include an anode, a cathode, and an organic emissive layer disposed between the anode and the cathode. The organic layer further comprises a ligand having the structure of FORMULA I, as described above.

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40.

In one aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl. In another aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.

Selections for the aromatic rings, metal, and substituents described as preferred for compounds comprising a ligand having FORMULA I are also preferred for use in a device that includes a compound comprising a ligand having FORMULA I. These selections include those for metal M, rings A and B, and substituents R_(A), R_(B), A₁, A₂, B₁, B₂, R₁, and R₂.

Preferably, at least one of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.

Preferably, the metal is Ir.

Preferably, A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine. Preferably, B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene.

In particular, the organic layer of the device may comprise a compound having a ligand selected from the group consisting of Formula II-VII, wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ is CD₃. Preferably, the organic layer comprises a compound selected from the group consisting of Compounds 2-42.

Additionally, the organic layer of the device may comprise a compound having a ligand selected from the group consisting of Formula II-VII, wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ includes CD₃.

Moreover, the organic layer of the device may comprise a compound having a ligand selected from the group consisting of Formula III-VIII. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be linked. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be fused. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ includes an alkyl group that includes CD, CD₂, or CD₃. Preferably, the organic layer comprises a compound selected from the group consisting of Compounds 43-82.

In one aspect, the organic layer is an emissive layer containing a compound provided herein wherein the compound is an emitting dopant. The organic layer may further comprise a host. Preferably, the host has the formula:

R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ may represent mono, di, tri, or tetra substitutions; and each of R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ is independently selected from the group consisting of hydrogen, alkyl and aryl. More preferably, the host is H1.

A consumer product comprising a device is also provided. The device comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer comprises a compound containing a ligand having the structure of FORMULA I, as described above.

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40.

Selections for the aromatic rings, metal, and substituents described as preferred for compounds comprising a ligand having FORMULA I are also preferred for use in a consumer product comprising device that includes a compound comprising a ligand having FORMULA I. These selections include those for metal M, rings A and B, and substituents R_(A), R_(B), A₁, A₂, B₁, B₂, R₁, and R₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

FIG. 3 shows the general structure of a ligand containing deuterium substitution.

FIG. 4 shows exemplary methyl-d3 substituted ligands.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, and a cathode 160. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. patent application Ser. No. 10/233,470, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink-jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

As used herein, the terms alkyl, aryl, and heteroaryl also include deuterium in place of hydrogen. For example, alkyl may include CH₃ or CD₃, and CH₂CH₃ or CH₂CD₃. Similarly, aryl and heteroaryl may include aromatic groups substituted with deuterium rather than hydrogen.

Replacing hydrogen with its isotope deuterium in iridium complexes has been reported in the literature (see, for example, U.S. Pub. No. 2008/0194853 and U.S. Pat. No. 6,699,599). Notably, deuterium atom substitution directly on the ring does not seem to provide color tuning. In particular, the inventors are not aware of any reports of a change in the emission profile of compounds substituted with deuterium atoms.

CD₃ substitution in a host material has also been reported (see, WO2008029670). However, the emission profile of an emitting dopant is an important property of the compound and substitution of a host material cannot provide any information regarding color tuning. In particular, the effect of deuterium substitution of the photoluminescence spectra (e.g., color tuning properties) cannot be assessed when the compound being modified is a host material rather than an emissive material, as provided herein. Therefore, emissive compounds having the beneficial properties of methyl substitution (i.e., color tuning, improved quantum efficiency and improved lifetime) as well as improved stability associated with deuterium may be desirable.

Methyl substitution of metal complexes has been shown to be useful for tuning the photophysical and electroluminescence properties of a compound. For example, methyl substitution at certain positions may be beneficial for its ability to improve the quantum efficiency, line shape, and improve the lifetime of an OLED.

Novel compounds are provided herein, the compounds comprising a ligand having a methyl-d3 substituent (illustrated in FIG. 3). In addition, particular ligands containing methyl-d3 substitution are also provided (illustrated in FIG. 4). Notably, both improved photoluminescence and improved device efficiency may be provided with the compounds disclosed.

Compounds provided herein comprise a ligand having a methyl-d3 substitution. These compounds may be advantageously used in an OLED to provide devices having improved efficiency, long lifetime and improved color (e.g., color tuning). Without being bound by theory, it is believed that the CD₃ substituent may improve stability because of the strong C-D bond. The strength of the C-D bond is greater than that of the C—H bond, as discussed above. Additionally, the smaller van der Waals radius of deuterium may translate into a less steric substituent (e.g., less twist on an aromatic ring containing a CD₃ substituent at the ortho position rather than a CH₃ substituent) and thus improved conjugation in a system having CD₃ substitution. Further, the reaction rate of a chemical process involving the C-D bond present in methyl-d3 may be slower due to the kinetic isotope effect. If the chemical degradation of an emissive compound involved breaking the methyl C—H bond, then the stronger C-D bond may improve the stability of the compound.

Methyl is the most simple alkyl substitution added as a modification to a compound. It may be a very important substitution group to modify the properties of both hosts and emitters in an OLED. Methyl can affect the packing properties in the solid state (i.e. sublimation property and charge transporting property), modify photophysical properties, and affect device stability. Methyl groups have been introduced to change the properties of tris(2-phenylpyridine)iridium (III) family. For example, the devices with tris(3-methyl-2-phenylpyridine)iridium(III) as an emitter have better stability than those devices with tris(2-phenylpyridine)iridium(III) as an emitter. In addition, the emission peak of tris(3-methyl-2-phenylpyridine)iridium(III) is red shifted about 10 nm. The evaporation temperature of tris(3-methyl-2-phenylpyridine)iridium (III) is also about 20 degrees lower than tris(2-phenylpyridine)iridium(III).

On the other hand, methyl is also considered reactive because of the benzylic protons. Without being bound by theory, the hydrogen atoms present in the methyl group may be especially reactive and thus may be the site of chemical degradation in the emissive compound. Further, it is well accepted in the field that during OLED operation the dopant compounds become oxidized. In the oxidized state, the benzylic position may become the weakest position to undergo further chemical degradation. The proposed mechanism may be more relevant when the emitting dopant is used with certain hosts, such as triphenylene/DBT hybrid materials, and less relevant with other hosts, such as Balq. Therefore, replacing the hydrogen atoms in the methyl group with deuterium atoms (methyl-d3) may stabilize the emissive compound.

It is believed that deuterium substitution can improve efficiency and stability because the atomic mass of deuterium is twice as great as that of hydrogen, which results in lower zero point energy and lower vibration energy level. Additionally, the chemical bond lengths and bond angles involving deuterium are different than those involving hydrogen. In particular, the van der Vaals radius of deuterium is smaller than that of hydrogen, because of the smaller stretching amplitude of the C-D bond compared to the C—H bond. Generally, the C-D bond is shorter and stronger than the C—H bond. Therefore, CD₃ substitution may provide the same color tuning and all of the advantages associated with increased bond strength (i.e., improved efficiency and lifetime).

As discussed above, deuterium substitution provides many benefits, e.g., increased efficiency and lifetime. Therefore, compounds comprising a ligand having deuterium substitution may be advantageously used in organic light emitting devices. Such compounds include, for example, compounds comprising a ligand having deuterium within an alkyl chain, e.g., C(D)(H)CH₃, CD₂CH₃ and CH₂CD₂CH₃, as well as deuterium at the end of an alkyl chain, e.g., CD₃.

Novel compounds are provided herein, the compounds comprise a ligand having the structure:

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. Preferably, A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine. Preferably, B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40. Preferably, the metal is Ir.

In one aspect, the ligand has the structure:

In one aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl. In another aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.

In one aspect, compounds are provided wherein at least 1 of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring conjugated or fused to ring A or ring B.

As discussed above, the substituents R_(A) and R_(B) may be fused to ring A and/or ring B. The substituents R_(A) and R_(B) may be any substituents, including substituents that are linked, fused to ring A and/or ring B or not fused to ring A and/or ring B.

In particular, compounds are provided comprising a ligand wherein the ligand is selected from the group consisting of:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; and at least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ is CD₃.

Additionally, compounds are provided comprising a ligand wherein the ligand is selected from the group consisting of:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; and at least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ includes CD₃.

Compounds comprising a ligand selected from the group consisting of:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; and R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be linked. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be fused. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ includes an alkyl group that includes CD, CD₂, or CD₃.

Specific examples of methyl-d3 substituted iridium complexes are provided, including compounds selected from the group consisting of:

Additional specific examples of deuterium substituted iridium complexes are provided, including compounds selected from the group consisting of:

In one aspect, compounds are provided wherein the compound comprises a ligand having Formula II, for example, Compounds 2-4.

In another aspect, compounds are provided wherein the compound comprises a ligand having Formula III, for example, Compounds 5-9.

In another aspect, additional compounds comprising a ligand having Formula III are provided, including Compounds 58, 59, 69-70, and 75-77.

In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula IV, for example, Compounds 10-14 and 27-40.

In another aspect, additional compounds comprising a ligand having Formula IV are provided, including Compounds 43-52, 62-67 and 80-82.

In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula V, for example, Compounds 15-19.

In another aspect, additional compounds comprising a ligand having Formula V are provided, including Compounds 55-57, 73, and 74.

In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula VI, for example, Compounds 20-23.

In another aspect, additional compounds comprising a ligand having Formula VI are provided, including Compounds 60, 61, 78 and 79.

In yet another aspect, Compounds are provided wherein the compound comprises a ligand having Formula VII, for example, Compounds 24-26, 41, and 42.

In a further aspect, compounds comprising a ligand having Formula III are provided, including Compounds 53, 54, 71 and 72.

The compounds comprising ligands having a formula selected from Formula II, Formula III, Formula IV, Formula V, Formula VI, and Formula VII may be particularly stable dopant compounds.

Additionally, compounds comprising ligands having Formula VIII may also be particularly stable compounds.

In one aspect, homoleptic compounds containing CD₃ are provided. In particular, compounds are provided wherein the ligand having FORMULA I is a ligand in a homoleptic compound. Homoleptic compounds provided herein include, for example, Compounds 2-19. In another aspect, heteroleptic compounds containing CD₃ are provided. In particular, compounds are provided wherein the ligand having FORMULA I is a ligand in a heteroleptic compound. Heteroleptic compounds provided herein include, for example, Compounds 20-42. Heteroleptic compounds containing CD₃ may include compounds having an emissive ligand and a non-emissive ligand, such as Compounds 20-26 which contain two emissive ligands and an acac ligand. In addition, heteroleptic compounds containing CD₃ may include compounds wherein all of the ligands are emissive ligand and the emissive ligands have different structures. In one aspect, heteroleptic compounds containing CD₃ may have 2 emissive ligands including CD₃ and one emissive ligand that does not contain CD₃. For example, Compounds 27, 33, 35-40. In another aspect, heteroleptic compounds containing CD₃ may have 1 emissive ligand including CD₃ and 2 emissive ligands that do not contain CD₃. For example, Compounds 29-32, 41, and 42. The emissive ligand including CD₃ may include a single CD₃ group (e.g., Compounds 29-32) or the ligand may include several CD₃ groups (e.g., Compounds 41 and 42 contain one emissive ligand with 2 CD₃ substituents). In yet another aspect, heteroleptic compounds containing CD₃ may contain 2 or more different types of emissive ligands wherein all ligands contain CD₃. For example, Compounds 28 and 34.

Additionally, an organic light emitting device is provided. The device comprises include an anode, a cathode, and an organic emissive layer disposed between the anode and the cathode. The organic layer comprises a compound containing ligand having the structure:

as described above. Selections for the aromatic rings, metal, and substituents described as preferred for compounds comprising a ligand having FORMULA I are also preferred for use in a device that includes a compound comprising a ligand having FORMULA I. These selections include those for metal M, rings A and B, and substituents R_(A), R_(B), A₁, A₂, B₁, B₂, R₁ and R₂.

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. Preferably, A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine. Preferably, B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40. Preferably, the metal is Ir.

In one aspect, the ligand has the structure:

In one aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl. In another aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.

In one aspect, compounds are provided wherein at least 1 of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.

As discussed above, the substituents R_(A) and R_(B) may be fused to ring A and/or ring B. The substituents R_(A) and R_(B) may be any substituents, including substituents that are linked, fused to ring A and/or ring B or not fused to ring A and/or ring B.

In particular, the organic layer of the device comprises a compound having a ligand selected from the group consisting of Formula R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ is CD₃. Preferably, the organic layer comprises a compound selected from the group consisting of Compounds 2-42.

Additionally, the organic layer of the device comprises a compound having a ligand selected from the group consisting of Formula II-VII. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ includes CD₃.

Moreover, the organic layer of the device may comprise a compound having a ligand selected from the group consisting of Formula III-VIII. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be linked. R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be fused. At least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ includes an alkyl group that includes CD, CD₂, or CD₃. Preferably, the organic layer comprises a compound selected from the group consisting of Compounds 43-82.

In one aspect, the organic layer is an emissive layer containing a compound provided having a ligand of FORMULA I, wherein the compound is an emitting dopant. The organic layer may further comprise a host. Preferably, the host has the formula:

R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ may represent mono, di, tri, or tetra substitutions; and each of R′₁, R′₂, R′₃, R′₄, R′₅, and R′₆ are independently selected from the group consisting of hydrogen, alkyl and aryl. More preferably, the host is H1.

A consumer product comprising a device is also provided. The device comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer comprises a compound containing a ligand having the structure:

as described above. Selections for the aromatic rings, metal, and substituents described as preferred for compounds comprising a ligand having FORMULA I are also preferred for use in a device that includes a compound comprising a ligand having FORMULA I. These selections include those for metal M, rings A and B, and substituents R_(A), R_(B), A₁, A₂, B₁, B₂, R₁ and R₂.

A and B may independently represent a 5-membered or 6-membered aromatic or heteroaromatic ring. Preferably, A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine. Preferably, B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene. A₁, A₂, B₁, and B₂ are independently C or N. R_(A) and R_(B) may represent mono, di, or tri substitutions. X_(A) and X_(B) are independently C or a heteroatom. R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl. At least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃. Preferably, at least one of R_(A), R_(B), R₁ and R₂ includes CD₃. R_(A), R_(B), R₁ and R₂ may be linked. R_(A), R_(B), R₁ and R₂ may be fused. The ligand is coordinated to a metal having an atomic weight greater than 40. Preferably, the metal is Ir.

In one aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl. In another aspect, X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.

The consumer product may comprise a device further comprising an organic layer containing a compound comprising a ligand having the structure selected from the group consisting of Formula II-VII. In particular, the compound may be selected from the group consisting of Compounds 2-42.

Moreover, the organic layer of the device may comprise a compound having a ligand selected from the group consisting of Formula III-VIII. Preferably, the organic layer comprises a compound selected from the group consisting of Compounds 43-82.

In one aspect, particular consumer products comprising a device are provided. Preferably, the device contains compounds wherein at least 1 of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.

As discussed above, the substituents R_(A) and R_(B) may be fused to ring A and/or ring B. The substituents R_(A) and R_(B) may be any substituents, including substituents that are linked, fused to ring A and/or ring B or not fused to ring A and/or ring B.

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED. Non-limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 1 below. Table 1 lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

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Experimental COMPOUND EXAMPLES EXAMPLE 1 Synthesis of Compound 10

Synthesis of 2-bromo-6-phenylpyridine. In a 3-neck 1 L round-bottom flask fitted with a condenser, nitrogen inlet, and 2 stoppers was added 2,6-dibromopyridine (15.3 g, 64.58 mmol), phenylboronic acid (7.87 g, 64.58 mmol), and potassium carbonate (17.85 g, 129.16 mmol) in 228 mL of dimethoxyethane and 150 mL of water. Nitrogen was bubbled directly into the mixture for 15 minutes. Tetrakis(triphenylphosphine)palladium (0) was added (1.85 g, 1.60 mmol) and the reaction mixture was heated to reflux. The reaction was complete after 3 h of heating. It was cooled to room temperature and diluted with water and ethyl acetate. The layers were separated and the aqueous layer extracted with ethyl acetate. The organic layers were dried over magnesium sulfate, filtered, and evaporated. The material was purified by column chromatography eluting with 2% ethyl acetate/hexanes followed by vacuum distillation using a Kugelrohr collecting product at 150° C. 5.2 g of product was obtained (34%)

Synthesis of 2-phenyl-6-methyl-d3-phenylpyridine. A 3-neck 500 mL round-bottom flask equipped with a dropping funnel, nitrogen inlet, and a stopper was dried by heating with a heat gun under vacuum. To the cooled, dry flask was added 2-bromo-6-phenylpyridine (11.3 g, 48.27 mmol) and 100 mL of dry THF. The solution was cooled in a dry ice/acetone bath under nitrogen and iodomethane-d₃ was added dropwise (6 mL, 96.54 mmol). The solution was stirred cold 1 h then allowed to warm to room temperature overnight. It was diluted with water and extracted twice with ethyl acetate. The organic layers were dried over magnesium sulfate, filtered and evaporated. The crude material was purified by column chromatography twice eluting with 2% ethyl acetate/hexanes. 5.8 g of 2-phenyl-6-methyl-d3-pyridine was obtained (70%).

Synthesis of Dimer. A mixture of 2-phenyl-6-methyl(d₃)pyridine (1.65 g, 9.58 mmol), iridium chloride (1.6 g, 4.35 mmol), and 30 mL of 2-ethoxyethanol were heated to reflux overnight under nitrogen. The mixture was cooled to room temperature and a red solid was filtered off. The solid was washed with methanol and hexanes and air dried in a fume hood. 1.09 g of product was obtained (44%) of dimer which was used as is in the next step.

Synthesis of triflate intermediate. A mixture was prepared of dimer (1.09 g, 0.956 mmol) and 125 mL dichloromethane in a 250 mL round-bottom flask. Silver triflate (0.51 g, 2.00 mmol) in 10 mL of methanol was added to the red mixture and it turned green. The contents of the flask were stirred overnight under nitrogen at room temperature. The mixture was filtered through a pad of Celite and the Celite rinsed with dichloromethane. The filtrate was evaporated to yield a greenish-yellow solid. The solid was dried under high vacuum. 1 g of solid was obtained (71%) and used as is in the next reaction.

Synthesis of Compound 10. In a 50 mL glass tube was added the triflate complex (1 g, 1.3 mmol) and 2-phenyl-6-methyl(d₃)pyridine (0.7 g, 4.0 mmol) and the tube was evacuated and replaced with nitrogen. This procedure was repeated and the tube subsequently heated to 200° C. under nitrogen overnight. The tube was cooled and dichloromethane was added to dissolve material to transfer to a flask. The crude material was purified by column chromatography eluting with 20, 40, and 50% dichloromethane/hexanes followed by sublimation at 250° C. 0.58 g of product was obtained (63%) after sublimation.

EXAMPLE 2 Synthesis of Compound 13

Synthesis of 3-methyl-d3-2-phenylpyridine. 3-bromo-2-phenylpyridine (9.9 g, 42 mmol) was dissolved in 100 mL of tetrahydrofuran and cooled to −78° C. To the solution was added BuLi (26.4 mL, 1.6 M in hexanes) dropwise. The reaction mixture was stirred at −78° C. for 1 h after the addition was complete. Methyl-d₃ iodide (9.3 g, 63 mmol) was added and warmed to room temperature for 2 h. The reaction was then quenched with water and extracted with ethyl acetate. The crude product was purified by column using hexanes and ethyl acetate as eluent. 2.3 g of pure product was obtained after purification.

Synthesis of Compound 13. 3-methyl-d3-2-phenylpyridine (1.8 g, 10.4 mmol) and Ir(acac)3 (0.64 g, 1.3 mmol) was heated up to 260° C. for 48 h under nitrogen. After cooled to room temperature, dichloromethane was added to dissolve the product. The dichloromethane solution was then poured into hexanes. The precipitate was collected and run through a silica gel plug. 0.6 g of product was obtained. The product was further purified by recrystallizing from 1,2-dichlorobenzene.

EXAMPLE 3 Synthesis of Compound 27

Synthesis of Compound 27. The triflate complex (1.4 g), 4-methyl-2,5-diphenylpyridine (1.5 g), and 50 mL of ethanol were mixed and heated up to reflux under nitrogen overnight. The precipitate was filtered. The crude material was purified by column chromatography eluting with 50% dichloromethane/hexanes. 1.1 g of desired product was obtained.

EXAMPLE 4 Synthesis of Compound 43

Synthesis of Compound 43. The Iridium triflate complex (1.0 g, 1.3 mmol) and 2-biphenyl-4-methylpyridine (1.0 g, 4 mmol) was place in a 100 mL round bottom flask. 20 mL of a 50:50 solution of ethanol and methanol was added to the flask. The reaction mixture was refluxed for 8 h. The reaction mixture was then allowed to cool to room temperature. The reaction mixture was poured onto a silica plug and was washed with ethanol followed by hexanes. The filtrate was discarded. The plug was then washed with dichloromethane to elute the product. The solvent from the filtrate was removed on the rotary evaporator. The product was further purified using column chromatography with 50:50 dichloromethane and hexanes as the eluent to yield 0.5 g (50% yield) of product.

EXAMPLE 5 Synthesis of Compound 50

Synthesis of Compound 50. The Iridium triflate complex (6.58 g, 9.2 mmol) and 4-(ethyl,d₃)-2,5-diphenylpyridine (6.58 g, 25.0 mmol) was place in a 1000 mL round bottom flask. 140 mL of a 50:50 solution of ethanol and methanol was added to the flask. The reaction mixture was refluxed for 8 h. The reaction mixture was then allowed to cool to room temperature. The reaction mixture was poured onto a silica plug and was washed with ethanol followed by hexanes. The filtrate was discarded. The plug was then washed with dichloromethane to elute the product. The solvent from the filtrate was removed on the rotary evaporator. The product was further purified using column chromatography with 50:50 dichloromethane and hexanes as the eluent to yield 3.8 g (54% yield) of product.

Device Examples

All devices are fabricated by high vacuum (<10⁻⁷ Torr) thermal evaporation. The anode electrode is 1200 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by 1000 Å of Al. All devices are encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H₂O and O₂) immediately after fabrication, and a moisture getter was incorporated inside the package.

Particular devices are provided wherein inventive compounds, Compound 10, Compound 13, and Compound 27, are the emitting dopant and H1 is the host. All device examples have organic stacks consisting of sequentially, from the ITO surface, 100 Å of E1 as the hole injecting layer (HIL), 300 Å of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) as the hole transport layer (HTL), 300 Å of H1, a host material, doped with 7% or 10% of the invention compound, as the emissive layer (EML), 50 Å of H1 as the blocking layer (BL) and 400 Å of Alq₃ (tris-8-hydroxyquinoline aluminum) as the ETL.

Comparative Examples 1-5 were fabricated similarly to the Device Examples, except the materials used in the EML and the BL differed. In particular, E1, E2, or E3 was used as the emitting dopant used in the EML of Comparative Examples 1 and 2, 3, 4 and 5, respectively. In addition, HPT was the BL material in Comparative Example 3.

As used herein, the following compounds have the following structures:

Particular materials for use in an OLED are provided. In particular, the materials may be used as emitting dopants in the emissive layer (EML) of such a device. The compounds provided herein may be used to improve color, efficiency, and lifetime in devices. Cmpd is an abbreviation of Compound. Ex. is an abbreviation of Example. Comp. is an abbreviation of Comparative.

TABLE 2 Example HIL HTL Host A % BL ETL Ex. 1 E1 100 Å NPD 300 Å H1 Cmpd 10 H1 50 Å Alq 400 Å  7% Ex. 2 E1 100 Å NPD 300 Å H1 Cmpd 10 H1 50 Å Alq 400 Å 10% Ex. 3 E1 100 Å NPD 300 Å H1 Cmpd 13 H1 50 Å Alq 400 Å  7% Ex. 4 E1100 Å NPD 300 Å H1 Cmpd 13 H1 50 Å Alq 400 Å 10% Ex. 5 E1 100 Å NPD 300 Å H1 Cmpd 27 H1 50 Å Alq 400 Å  7% Ex. 6 E1 100 Å NPD 300 Å H1 Cmpd 27 H1 50 Å Alq 400 Å 10% Comp. Ex. 1 E1 100 Å NPD 300 Å H1 E1 H1 50 Å Alq 400 Å  7% Comp. Ex. 2 E1 100 Å NPD 300 Å H1 E1 H1 50 Å Alq 400 Å 10% Comp. Ex. 3 E1 100 Å NPD 300 Å H2 E2 HPT 50 Å Alq 400 Å 10% Comp. Ex. 4 E1 100 Å NPD 300 Å H1 E3 H1 50 Å Alq 400 Å  7% Comp. Ex. 5 E1 100 Å NPD 300 Å H1 E3 H150 Å Alq 400 Å 10%

TABLE 3 At 1000 nits At 40 mA/cm² λ_(max), FWHM CIE V LE EQE PE Lo, RT_(80%) Example nm nm X Y (V) (cd/A) (%) (lm/W) nits (h) Ex. 1 510 70 0.290 0.622 5.7 48.7 14.2 26.7 14,486 76 Ex. 2 512 68 0.282 0.629 5.2 51.6 14.9 31.2 16,186 67 Ex. 3 527 76 0.349 0.610 6.1 54.1 14.9 28.1 15,179 204 Ex. 4 527 75 0.350 0.611 5.6 54.3 15 30.2 15,810 220 Ex. 5 522 68 0.329 0.623 5.4 66.6 18.2 38.6 18,557 174 Ex. 6 526 72 0.342 0.616 4.9 66.5 18.1 42.7 19,885 184 Comp. Ex. 1 527 72 0.341 0.617 6 55.6 15.2 29.1 16,066 165 Comp. Ex. 2 527 79 0.344 0.614 6.4 56.7 15.6 27.6 15,436 155 Comp. Ex. 3 507 68 0.294 0.615 5.8 44.2 13.1 23.9 13,930 14 Comp. Ex. 4 522 66 0.328 0.624 5.5 65 17.8 37.3 18,170 116 Comp. Ex. 5 526 72 0.340 0.616 5.1 65.3 17.9 40.4 19,740 128

From Device Examples 1-6, it can be seen that the CD₃ compounds provided herein as emitting dopants provide long lifetime. In particular, the lifetime, RT_(80%) (defined as the time required for the initial luminance, L₀, to decay to 80% of its value, at a constant current density of 40 mA/cd² at room temperature) of Device Examples containing the compounds provided are notably higher than Comparative Examples, which contain the corresponding CH₃ substituted compounds. Specifically, Compound 13 used in Device Examples 3 and 4 provided RT_(80%) of 204 h and 220 h, respectively, as compared to RT_(80%) of 165 h and 155 h for Comparative Examples 1 and 3, which used the corresponding CH₃ substituted compound (E1).

The data above also demonstrates that heteroleptic CD₃ containing compounds provided herein may provide devices having improved lifetime and efficiency. In particular, Device Examples 5 and 6 containing Compound 27 provide better lifetime and efficiency than Comparative Examples 4 and 5, which contain the corresponding CH₃ substituted compound (E3). Specifically, Compound 27 provided RT_(80%) of 174 h and 184 h as compared to RT_(80%) of 116 h and 128 h for the corresponding methyl-substituted compound E3.

Additionally, the methyl-d3 substituted compounds provided devices with improved efficiency. In particular, Compounds 10, 13 and 27 achieved an operating voltage lower than that of the Comparative Examples using corresponding CH₃ substituted compounds. Specifically, Compounds 10, 13, and 27 provide an operating voltage (V) of 5.2 V, 5.6 V, and 4.9 V compared to 6.4 V, 5.8 V, and 5.1 V, respectively.

The data above suggests that the methyl-d3 substituted compounds provided herein can be excellent emitting dopants for phosphorescent OLEDs. These compounds provide devices with improved color, efficiency and lifetime.

As used herein, the following compounds have the following structures:

TABLE 4 Example HIL HTL Host A % BL ETL Ex. 7 E5 100 Å NPD 300 Å H1 Cmpd 43 H1 100 Å Alq 400 Å  7% Ex. 8 E5 100 Å NPD 300 Å H1 Cmpd 43 H1 100 Å Alq 400 Å 10% Comp. Ex. 6 E1100 Å NPD 300 Å H1 E4 H1 100 Å Alq 400 Å  7% Comp. Ex. 7 E1 100 Å NPD 300 Å H1 E4 H1 100 Å Alq 400 Å 10%

TABLE 5 At 1000 nits At 40 mA/cm² λ_(max), FWHM CIE V LE EQE PE Lo, RT_(80%) Example nm nm X Y (V) (cd/A) (%) (lm/W) nits (h) Ex. 7 534 62 0.368 0.604 6.1 63.3 17.2 32.7 14,037 374 Ex. 8 534 64 0.380 0.597 5.3 69 18.8 40.7 18,702 365 Comp. Ex. 6 534 64 0.380 0.596 5.7 68 18.6 37.3 17,776 212 Comp. Ex. 7 534 64 0.380 0.597 5.3 68.8 18.8 40.5 19,306 283

As can be seen from Device Examples 7 and 8, Compound 43 has comparable efficiency and color against E4, and the device lifetime was much longer. Device Example 7 showed LT₈₀ of 374 h and Comparative Example 6 showed lifetime of 212 h. Device Example 8 showed LT₈₀ of 365 h and Comparative Example 7 showed lifetime of 283 h. The device data shows that the methyl-d3 substituted compounds provided may improve device lifetime.

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore includes variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting. 

1. A compound comprising a ligand having the structure:

wherein A and B may independently represent a 5-membered or 6-membered aromatic ring; wherein A₁, A₂, B₁, and B₂ are independently C or N; wherein R_(A) and R_(B) may represent mono, di, or tri substitutions; wherein X_(A) and X_(B) are independently C or a heteroatom; wherein R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; wherein at least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃; wherein R_(A), R_(B), R₁ and R₂ may be linked; wherein R_(A), R_(B), R₁ and R₂ may be fused; and wherein the ligand is coordinated to a metal having an atomic weight greater than
 40. 2. The compound of claim 1, wherein the ligand has the structure:


3. The compound of claim 2, wherein at least one of R_(A), R_(B), R₁ and R₂ includes CD₃.
 4. The compound of claim 1, wherein at least one of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.
 5. The compound of claim 1, wherein X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl.
 6. The compound of claim 1, wherein X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is phenyl further substituted with a group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl and wherein the group includes at least one of CD, CD₂ or CD₃.
 7. The compound of claim 1, wherein the ligand is selected from the group consisting of:

wherein M is Ir; wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; and wherein at least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ includes CD₃.
 8. The compound of claim 1, wherein the ligand is selected from the group consisting of:

wherein M is Ir; wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; and R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be linked; wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ may be fused; and wherein at least one of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ includes an alkyl group that includes CD, CD₂, or CD₃.
 9. The compound of claim 1, wherein A is selected from the group consisting of imidazole, pyrazole, triazole, oxazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, and triazine.
 10. The compound of claim 1, wherein B is selected from the group consisting of benzene, pyridine, furan, pyrrole, and thiophene.
 11. The compound of claim 1, wherein the metal is Ir.
 12. The compound of claim 1, wherein the ligand having FORMULA I is a ligand in a homoleptic compound.
 13. The compound of claim 1, wherein the ligand having FORMULA I is a ligand in a heteroleptic compound.
 14. An organic light emitting device comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, wherein the organic layer comprises a compound further comprising a ligand having the structure:

wherein A and B may independently represent a 5-membered or 6-membered aromatic ring; wherein A₁, A₂, B₁, and B₂ are independently C or N; wherein R_(A) and R_(B) may represent mono, di, or tri substitutions; wherein X_(A) and X_(B) are independently C or a heteroatom; wherein R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; wherein at least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃; wherein R_(A), R_(B), R₁ and R₂ may be linked; wherein R_(A), R_(B), R₁ and R₂ may be fused; and wherein the ligand is coordinated to a metal having an atomic weight greater than
 40. 15. The device of claim 14, wherein at least one of the substituents of R_(A) and R_(B) is CD₃ attached directly to ring A, ring B, or a ring that is conjugated or fused to ring A or ring B.
 16. The device of claim 14, wherein X_(A) and X_(B) are independently C or N and when X_(A) is N, R₁ is aryl.
 17. The device of claim 14, wherein the organic layer is an emissive layer and the compound is an emitting dopant.
 18. The device of claim 17, wherein the organic layer further comprises a host.
 19. A consumer product comprising a device, the device further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, wherein the organic layer comprises a compound further comprising a ligand having the structure:

wherein A and B may independently represent a 5-membered or 6-membered aromatic ring; wherein A₁, A₂, B₁, and B₂ are independently C or N; wherein R_(A) and R_(B) may represent mono, di, or tri substitutions; wherein X_(A) and X_(B) are independently C or a heteroatom; wherein R_(A), R_(B), R₁ and R₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; wherein at least one of R_(A), R_(B), R₁ and R₂ includes CD, CD₂ or CD₃; wherein R_(A), R_(B), R₁ and R₂ may be linked; wherein R_(A), R_(B), R₁ and R₂ may be fused; and wherein the ligand is coordinated to a metal having an atomic weight greater than
 40. 20. The consumer product of claim 19, wherein the consumer product is selected from the group consisting of flat panel displays, computer monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a wall, theater or stadium screen, and a sign. 